Air streams can carry contaminant material therein. In many instances, it is desired to filter some or all of the contaminant material from the air stream. For example, air flow streams to engines (for example combustion air) for motorized vehicles or for power generation equipment, gas streams to gas turbine systems and air streams to various combustion furnaces, carry particulate contaminant therein that should be filtered. It is preferred for such systems, that selected contaminant material be removed from (or have its level reduced in) the air. A variety of air filter arrangements have been developed for contaminant rejection. In many instances, especially where government regulations require, it is also desired to measure the mass flow rate of the filtered air that will be delivered. In some applications, it is desirable to include an air metering device within the air filter arrangement. However, other components within the filter arrangement often cause excessive turbulence thereby minimizing the accuracy of the measured airflow for such a configuration. Improvements are sought.